PCI: imx6: Assert ref_clk_en after reference clock stabilizes on i.MX95

According to the PHY Databook Common Block Signals section, the
ref_clk_en signal must remain de-asserted until the reference clock is
running at the appropriate frequency. Once the clock is stable,
ref_clk_en can be asserted. For lower power states where the reference
clock to the PHY is disabled, ref_clk_en should also be de-asserted.

Move the ref_clk_en bit manipulation into imx95_pcie_enable_ref_clk()
to ensure the reference clock stabilizes before ref_clk_en is asserted
and before the PHY reset is de-asserted. This aligns with the timing
requirements specified in the PHY documentation.

Fixes: d8574ce57d76 ("PCI: imx6: Add external reference clock input mode support")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260518072715.3166514-3-hongxing.zhu@nxp.com

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index b32748816ac8674c6e919a605e78c785e9979b5b..cce78a7a1624569a2c492290a99c898fde660596 100644 (file)
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -270,8 +270,6 @@ static int imx95_pcie_select_ref_clk_src(struct imx_pcie *imx_pcie)
 
 static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
 {
-       bool ext = imx_pcie->enable_ext_refclk;
-
        /*
         * ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
         * Through Beacon or PERST# De-assertion
@@ -290,10 +288,6 @@ static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
                        IMX95_PCIE_PHY_CR_PARA_SEL,
                        IMX95_PCIE_PHY_CR_PARA_SEL);
 
-       regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_0,
-                          IMX95_PCIE_REF_CLKEN,
-                          ext ? 0 : IMX95_PCIE_REF_CLKEN);
-
        return 0;
 }
 
@@ -742,7 +736,29 @@ static void imx95_pcie_clkreq_override(struct imx_pcie *imx_pcie, bool enable)
 
 static int imx95_pcie_enable_ref_clk(struct imx_pcie *imx_pcie, bool enable)
 {
+       bool ext = imx_pcie->enable_ext_refclk;
+
        imx95_pcie_clkreq_override(imx_pcie, enable);
+       /*
+        * The ref_clk_en signal must remain de-asserted until the
+        * reference clock is running at appropriate frequency, at which
+        * point this bit can be asserted. For lower power states where
+        * the reference clock to the PHY is disabled, it may also be
+        * de-asserted.
+        * +------------------- -+--------+----------------+
+        * | External clock mode | Enable | PCIE_REF_CLKEN |
+        * +---------------------+--------+----------------+
+        * | TRUE                | X      | 1b'0           |
+        * +---------------------+--------+----------------+
+        * | FALSE               | TRUE   | 1b'1           |
+        * +---------------------+--------+----------------+
+        * | FALSE               | FALSE  | 1b'0           |
+        * +---------------------+--------+----------------+
+        */
+       regmap_update_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_0,
+                          IMX95_PCIE_REF_CLKEN,
+                          ext || !enable ? 0 : IMX95_PCIE_REF_CLKEN);
+
        return 0;
 }